Image compression apparatus, method and recording medium storing an image compression program

ABSTRACT

An image compression apparatus and method, and a carrier wave encoded with a computer readable control program having instructions for use by a computer, perform an image compression process. A compression level is determined for use in compressing a picture image to a predetermined target data amount by iteratively compressing a reduced version of the picture image in order to determine the compression level that is to be used to compress the picture image. First, a reduced-size picture image is created from the picture image that is to be compressed. A preliminary compression target data amount is then derived, for example, based on the target data amount, the data amount of the picture image and the data amount of the reduced-size picture image. The reduced-size picture image is then compressed using a compression level. The size of the resulting compressed reduced-size picture image is compared to the preliminary compression target data amount. The compression level is then adjusted (raised or lowered) and compression of the reduced-size picture image is repeated until the resulting compressed reduced-size picture image satisfies the preliminary compression target data amount. The compression level that ultimately is derived, is then used to compress the picture image. The resulting compressed picture image will then satisfy the predetermined target data amount.

RELATED PROVISIONAL APPLICATION

This is a Continuation of application Ser. No. 10/114,067 filed Apr. 3,2003 now abandoned, which in turn is a Continuation of application Ser.No. 09/861,552 filed May 22, 2001 now abandoned which in turn is aContinuation of application Ser. No. 09/088,365 filed Jun. 2, 1998 nowabandoned. The entire disclosure of the prior application(s) is herebyincorporated by reference herein in its entirety.

This nonprovisional application claims the benefit of ProvisionalApplication No. 60/057,680, filed Aug. 29, 1997.

INCORPORATION BY REFERENCE

The disclosure of the following priority application is hereinincorporated by reference: Japanese Patent Application No. 9-146365,filed Jun. 4, 1997.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to an image compression apparatus thatcompresses an image, particularly a picture image, and to a compressionmethod and recording medium storing a computer readable compressionprogram.

2. Description of Related Art

In recent years, there have been great advances in image compressiontechnology to compress digital image compression signals. For example,compression methods such as the JPEG (Joint Photographic Experts Group)and the MPEG (Moving Picture Experts Group) methods are known,international standards for compressing digital still picture images andmoving picture images.

These compression methods perform picture image compression byperforming the following processes in the order: Discrete CosineTransformation (DCT), followed by linear quantization, followed byvariable-length coding.

Picture image compression first divides the picture image into blocksof, for example, 8×8 picture elements, and directly transforms eachblock of the picture image using DCT. The DCT separates the pictureimage signal into the portion that is necessary for viewing (thatportion of the picture image having low frequency components), and intothe portion that is not necessary for viewing (that portion of thepicture image having high frequency components).

Next, quantization is performed by means of frequency weightedquantization. Frequency weighted quantization is a method that quantizesby changing the quantization amount in accordance with the frequency.Since the picture image data is transformed into frequency coefficientsby the DCT, for example, the quantization amount is increased for thehigh frequency components that are not necessary for viewing, therebyreducing the data amount. The quantization amount is made smaller forthe low frequency components that are necessary for viewing, therebycontrolling the deterioration of the picture image.

Next, variable length code (VLC) such as, for example, Huffman encodingor so forth is applied. Huffman encoding, by assigning variable lengthcode according to the frequency by which data is generated, encodes byassigning code with the shortest bit length to the data with the highestfrequency of occurrence, thereby reducing the data amount.

With the picture image compression processing described above, thecompression efficiency varies according to the amount of spatialredundancy of the particular picture image. In other words, a pictureimage having high spatial redundancy (for example, a natural pictureimage with low contrast) is appropriate for picture image compressionbecause it can attain high compression efficiency. On the other hand, apicture image having little or no spatial redundancy (for example,computer graphics with high contrast) is not suitable for picture imagecompression because the compression efficiency (using JPEG or MPEG, forexample) is low.

Depending upon the amount of this type of spatial redundancy, thepost-compression file size varies greatly even when undergoing thecompression process at the same compression level.

The electronic still camera is one primary example of a device that cansuffer from this ill effect. The electronic still camera compresses aphotographed picture image, input by means of a CCD, and records it innon-volatile memory. Normally, it is possible to compress and recordseveral 10 s of photographic picture images (e.g., 20–60 images).However, when the post-compression file size varies greatly for eachphotographic picture image, it becomes impossible to know with certaintyhow many picture images can be recorded in a particular memory.

For this purpose, electronic still cameras have been proposed to unifyand record the post-compression file size. With these cameras, a pictureimage undergoes compression processing so as to become a standard filesize. For example, in the case of compressing a photographic pictureimage so as to have a unified file size of 100 KB, first, compressionprocessing is performed at a certain compression level. If thecompression result is larger than 100 KB, the compression level israised and the compression process is repeated. If the compressionresult is smaller than 100 KB, then the compression level is lowered andthe compression process is repeated.

By repeating the compression process by appropriately changing thecompression level in this way, the photographic picture image iscompressed to a standard file size. However, generally, since the filesize of a photographic picture image is large, the computation time ofcompression processing is increased, creating a problem in that a longtime is required until the photographic picture image can be compressedto the standard size.

SUMMARY OF THE INVENTION

The invention relates to an image compression apparatus and method, andto a carrier wave (that can be recorded, for example, on a recordingmedium) encoded with a computer readable control program havinginstructions for use by a computer to perform the image compressionprocess. According to one aspect of the invention, a compression levelis determined for use in compressing a picture image to a predeterminedtarget data amount by iteratively compressing a reduced version of thepicture image in order to determine the compression level that is to beused to compress the picture image.

First, a reduced-size picture image is created from the picture imagethat is to be compressed. The reduced-size picture image has some, butnot all, of the picture elements from the picture image. Thus, thereduced-size picture image has fewer picture elements than the pictureimage. T he reduced-size picture image can be created by extracting afield picture image from the full-size (or frame) picture image and/orby producing a thumbnail picture image from the full-size picture image.

A preliminary compression target data amount is then derived, forexample, based on the target data amount, the data amount of the pictureimage and the data amount of the reduced-size picture image. Forexample, the preliminary compression target data amount can be derivedby multiplying the target data amount by a ratio between the size of thereduced-size picture image and the full-size picture image.

The reduced-size picture image is then compressed using a compressionlevel. The size of the resulting compressed reduced-size picture imageis then compared to the preliminary compression target data amount. Thecompression level is then adjusted (raised or lowered) and compressionof the reduced-size picture image is repeated until the resultingcompressed reduced-size picture image satisfies the preliminarycompression target data amount.

The compression level that ultimately is derived, is then used tocompress the picture image. The resulting compressed picture image willthen satisfy the predetermined target data amount.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with the followingdrawings in which like reference numerals designate like elements andwherein:

FIG. 1 is a high-level functional diagram of one aspect of theinvention;

FIG. 2 is a block diagram of a camera according to a first embodiment ofthe invention;

FIG. 3 is a perspective view of the FIG. 2 camera;

FIG. 4 is a flow chart of a main routine performed by a camera of thefirst embodiment;

FIG. 5 is a flow chart of a release routine performed by a camera of thefirst embodiment;

FIG. 6 is a flow chart of a recording routine performed by a camera ofthe first embodiment;

FIG. 7 is a flow chart of a read routine performed by a camera of thefirst embodiment;

FIG. 8 illustrates the relationship between the compression level andthe expected compression ratio;

FIG. 9 illustrates the picture image compression process of the firstembodiment;

FIG. 10 is a block diagram of a camera according to a second embodimentof the invention;

FIG. 11 is a block diagram of a camera according to a third embodimentof the invention;

FIG. 12 is a flow chart of a main routine performed by the camera of thethird embodiment;

FIG. 13 is a flow chart of a release routine performed by the camera ofthe third embodiment;

FIG. 14 is a flow chart of a recording routine performed by the cameraof the third embodiment;

FIG. 15 is a first part of a flow chart of a single-view displayroutine;

FIG. 16 is a second part of a flow chart of the single-view displayroutine;

FIG. 17 illustrates thumbnail picture image creation; and

FIG. 18 illustrates the thumbnail picture image selection process and aplurality of thumbnail picture images displayed on a display screen.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a high-level representation of one aspect of the invention. Anelectronic camera includes a number of functional portions orsub-sections, referred to in FIG. 1 as “means.” As will become clearfrom the ensuing description, each means is not necessarily a separateor separable unit or component of the camera. There can be overlapbetween the actual structure and software of the camera that performs(or corresponds to) the various means. For example, a singlemicroprocessor can function as parts of (or all of) more than one of theillustrated means. Alternatively, it is possible to use separate,dedicated microprocessors for each means that relies on microprocessorcontrol.

One aspect of the invention relates to a picture image compressionapparatus that compresses the data of a picture image to a predeterminedtarget data amount. A picture image creation means 1 creates, from apicture image (e.g., a digital image input through a CCD), areduced-size picture image having a reduced number of picture elementscompared to the picture image. A data amount determination means 2derives, using the target data amount, a preliminary compression targetdata amount, which is the target data amount of the reduced-size pictureimage. A preliminary compression means 3 derives a compression levelwhen the data amount of the compressed reduced-size picture imagematches the preliminary compression target data amount. Preliminarycompression means 3 derives the compression level by repeating acompression operation after changing the compression level forcompressing the data of the reduced-size picture image until thepreliminary compression target data amount is reached. Then, compressionmeans 4 compresses the data of the picture image to the target dataamount according to the compression level derived from the preliminarycompression means 3.

The picture image creation means 1 can create a field picture image asthe reduced-size picture image from a frame picture image. The pictureimage creation means 1 can create a thumbnail picture image as thereduced-size picture image in order to display the thumbnail pictureimage in a single-view display.

Another aspect of the invention relates to a method of compressing apicture image and to a carrier wave encoded with a computer readableprogram that includes instructions for causing a computer to compress apicture image as detailed above. The carrier wave can be recorded on arecording medium such as, for example, a CD ROM. The program includes anumber of instructions. One instruction is to create from a pictureimage, a reduced-size picture image having a reduced number of pictureelements compared to the picture image. Another instruction is to derivea preliminary compression target data amount, which is the postcompression data amount of the reduced-size picture image. This isderived using a predetermined target data amount, which is thepost-compression data amount of the picture image, and by comparing thedata amount of the picture image and the data amount of the reduced-sizepicture image. Another instruction is to derive a compression level whenthe post-compression data amount of the compressed reduced-size imagematches the preliminary compression target data amount. The compressionlevel is derived by repeating compression after changing the compressionlevel for the data of the reduced-size picture image. A finalinstruction is to compress the data of the picture image to the targetdata amount according to the derived compression level.

With the picture image compression apparatus and method outlined above,first the picture image creation means 1 creates the reduced-sizepicture image, which has a reduced number of picture elements from thepicture image. This is done before compressing the data of the pictureimage.

The data amount determination means 2 then derives the preliminarycompression target data amount, which is the target data amount forcompression of the reduced-size picture image. The preliminarycompression target data amount is derived from the target data amount ofthe picture image according to the ratio of the picture image to thereduced-size picture image. However, the data amount determination means2 may also derive this amount directly, or it may be calculated byanother means and set in advance into the data amount determinationmeans 2.

The preliminary compression means 3 changes the compression levelrelative to the data of the reduced-size picture image, and repeatsexecution of the compression process (of the reduced-size picture image)until it derives the final compression level, which is the compressionlevel at the time that the data of the reduced-size picture image iscompressed to a size corresponding to the preliminary compression targetdata amount.

The compression means 4 executes, according to the final compressionlevel, the main compression (of the picture image) so that the data ofthe picture image becomes compressed to the predetermined target dataamount.

According to one option, the picture image creation means 1 extracts thefield picture image as a reduced-size picture image from the framepicture image by means of a thinning process of the picture image data.For example, every other scan line can be ignored (thinned out).

According to another option, the picture image creation means 1 createsthe reduced-size picture image by producing a thumbnail picture image inorder to display the picture image as a single-view display.

Embodiments of the present invention are described hereafter withreference to the drawings. In the present embodiment, an example of anelectronic still camera will be given as a description of a device thatuses the picture image compression apparatus of the present invention.FIG. 2 is a block diagram of an electronic still camera that is a firstembodiment of the invention. FIG. 3 is a perspective view of the cameraof the first embodiment.

In FIG. 2, the main body 21 is connected to a camera component 22. Theinternal components of the camera component 22 include a photographiclens 23 and a CCD sensor 24 arranged in a position to receivetransmitted light of the photographic lens 23. The photo-electric signalof the CCD sensor 24 is input, through an A/D converter 25, into apicture image memory 26, which is arranged within the main body 21.

The output of the picture image memory 26 is input through an encoder 27into a video selection switch 28. The output of the video selectionswitch 28 is input into a monitor 29 or into a video terminal 30.

Meanwhile, the input/output terminal of the picture image memory 26 isconnected to a first input/output terminal of a picture image processingcircuit 31, which is arranged within the main body 21. A secondinput/output terminal of the picture image processing circuit 31 isconnected to an input/output terminal of a picture image processingmemory 32.

The picture image processing memory 32 is connected to a flash memory 35through a JPEG circuit 33 and a data transfer component 34. Flash memory35 can be a card type of memory that has the ability to be attached andremoved freely from the main body 21.

Picture image data can be transferred in both directions between thepicture image processing memory 32 and the flash memory 35.

CPU 36 also is arranged within the main body 21. The control signal ofthe CPU 36 is input into the CCD sensor 24, the encoder 27, the pictureimage processing circuit 31, the JPEG circuit 33 and the data transfercomponent 34. In addition, the output signals of the JPEG circuit 33,the data transfer component 34 and the operation switch 37 are inputinto the CPU 36.

The corresponding relationship between the high-level representation ofFIG. 1 and the first embodiment is as follows. The picture imagecreation means 1 corresponds to the CCD sensor 24, the A/D converter 25and the picture image memory 26. The data amount determination means 2corresponds to the CPU 36. The preliminary compression means 3corresponds to the JPEG circuit 33. The compression means 4 alsocorresponds to the JPEG circuit 33.

A description of the operation of the first embodiment is providedhereafter, with reference to the drawings. FIG. 4 through FIG. 7 areflow charts describing the operation of the first embodiment. Inaddition, FIG. 9 illustrates the picture image compression process ofthe present embodiment.

When the power switch (not shown in the figure) is switched ON, the CPU36 executes the following operation according to the camera sequenceprogram stored in internal ROM. The CPU 36 initializes the system afterclearing the picture image memory 26 and the picture image processingmemory 32. The start photography command is input from the CPU 36 intothe CCD sensor 24 and photography begins (step S1 of FIG. 4).

The photographic object obtained through the photographic lens 23 isformed on the CCD sensor 24 and converted photo-electrically. Thephoto-electric signal, by reading every other scanning line includes twofield signals in a time series as is well known. In other words, an evennumber field signal and an odd number field signal that have a reducednumber of picture elements in the vertical direction are output. Thesesignals together comprise, in the same manner as the video signal, oneframe of image data. The one frame has two fields, one with an evennumber field signal and one with an odd number field signal.

The A/D converter 25 increases the width of the even number field signaland the odd number field signal respectively, and then converts them toa digital video signal. In the picture image memory 26, the digitalvideo signal is accumulated in the order received, and hence the evennumber field picture image and the odd number field picture image arecreated.

The encoder 27 chronologically reads the even number field picture imageand the odd number field picture image that are stored in the pictureimage memory 26, and then D/A converts them to an analog projected imagesignal, and outputs them to the video terminal 30 or to the monitor 29that is selected by the video selection switch 28.

In this instance, the monitor 29 is selected. The monitor 29, which is,for example, a liquid crystal display monitor, A/D converts the analogprojected image signal, combines the even number field picture image andthe odd number field picture image, integrates the frame picture imageand performs display by means of the active matrix method.

Through the operation described above, the picture image is taken-inregularly and is chronologically displayed on the monitor 29.

In this state, the CPU 36 determines whether the release switch SW1 ofthe operation switch 37 has been pressed. If the release switch SW1 ispressed (step S2 in FIG. 4), the following release routine is executed(step S3 in FIG. 4).

The CPU 36 outputs the stop output command of the analog projected imagesignal to the encoder 27. The encoder 27 stops reading the field pictureimage that is stored in the picture image memory 26, and temporarilystops the output of the analog projected image signal to the monitor 29(step S11 in FIG. 5). Next, at the moment that the release switch SW1 ispressed, the image formed on the CCD sensor 24 is photo-electricallyconverted and accumulated to the picture image memory 26 through the A/Dconverter 25 (step S 12 in FIG. 5). The CPU 36 outputs the restartoutput command of the analog projected image signal to the encoder 27,and the encoder 27 reads the even number field picture image and the oddnumber field picture image that are stored in the picture image memory26, and A/D converts each to the analog projected image signal, and thenoutputs this to the monitor 29 (step S13 in FIG. 5).

According to the operation described above, the operator has the abilityto take in a picture image at the moment there is a photographicopportunity by pressing the release switch SW1.

Next, a description of the operation that records the taken pictureimage into the flash memory 35 will be described hereafter.

The CPU 36 determines whether the recording switch SW2 of the operationswitch 37 is pressed. When the recording switch SW2 is pressed (step S4of FIG. 4), the following recording routine is executed (step S5 in FIG.4).

The picture image processing circuit 31, in accordance with the fieldpicture image reading command supplied from the CPU, reads one of thefields (either the even number field picture image or the odd numberfield picture image) that are accumulated in the picture image memory26, and transfers it to the picture image processing memory 32 (step S21of FIG. 6).

The CPU 36, for example, can be set in advance so as to compress aseveral MB (megabyte) frame picture image to a target data amount ofabout 100 KB (kilobytes). In addition, since the field picture imagebecomes the data amount of ½ of the frame picture image, the CPU 36 canbe set in advance so as to compress the field picture image to apreliminary compression target data amount of 50 KB. The JPEG circuit 33repeats the compression process until the field picture image that isstored in the picture image processing memory 32 becomes the preliminarycompression target data amount.

In this instance, a description of a specific numerical value will begiven relative to the preliminary compression process. For example, thedata amount of the field picture image is 500 KB (with a frame pictureimage of 1 MB). Stored in advance in the internal ROM of the JPEGcircuit 33 is the relationship between the compression ratio that isexpected (hereafter referred to as the expected compression ratio) andthe compression level that the standard picture image is subject to. Agraph of this is shown in FIG. 8. In this instance, the expectedcompression ratio that corresponds to the compression levels 1 through99 is indicated.

A preliminary compression target data amount and a preliminarycompression initiation command are transferred from the CPU 36 to theJPEG circuit 33. The JPEG circuit 33, in accordance with such command,reads the field picture image that is stored in the picture imageprocessing memory 32 and begins the compression. In particular, JPEGcircuit 33 reads the data amount of the field picture image that isstored in the picture image processing memory 32 and compresses suchdata amount so that it matches the preliminary compression target dataamount. In this instance, since a 500 KB data amount must be compressedso as to become 50 KB, first, compression is performed at a compressionlevel of 30 (expected compression ratio 10%). The picture imagecompression is performed by performing the following procedure in thefollowing order: DCT, followed by linear quantization, followed byvariable length coding (step S22 in FIG. 6). JPEG circuit 33 repeats thecompression process by changing the compression level until thecompression result is within a range of 50 KB± an allowable value,thereby deriving the compression level when arriving within this range(steps S23 and S24 of FIG. 6).

For example, when the compression result is 40 KB, since the compressionlevel is too large and there is the possibility that the picture imagewill deteriorate upon reproduction, the compression level is lowered. Inthis instance, this is derived by the following expression (1):(Expected compression ratio for the next time)=(the expected compressionratio of the previous time)×(preliminary compression target dataamount)/(data amount of the compression result of the previoustime)  (1)

According to expression (1), an expected compression ratio for the nexttime is computed to be 12.5%, and the JPEG circuit 33 performscompression again at the compression level that corresponds to theexpected compression ratio. It then determines whether the compressionresult has become 50 KB.

In addition, when the compression result is 60 KB, since the compressionlevel is too small, an expected compression ratio of 8.3% is computed.Then, the compression is performed again at the compression level thatcorresponds to this expected compression ratio, and it is determinedwhether the compression result has become 50 KB.

The change of the compression level can be executed by changing thequantization amount. More specifically, in the internal ROM of the JPEGcircuit 33, a quantization table of differing quantization amounts isprepared in advance for each compression level, and this quantizationtable is appropriately used.

The JPEG circuit 33 repeats the feed back process described above, andthe compression level that compresses the field picture image to thepreliminary compression target data amount is derived and transferred tothe CPU 36. The CPU 36 stores that compression level in the internalmemory (step S25 of FIG. 6).

Next, the picture image processing circuit 31, by means of the framepicture image creation command from the CPU 36, reads the even numberfield picture image and the odd number field picture image that areaccumulated in the picture image memory 26, and integrates the framepicture image from the combined two field picture images (step S26 ofFIG. 6)

The picture image processing circuit 31 transfers the frame pictureimage to the picture image processing memory 32. The JPEG circuit 33,according to the start main compression command from the CPU 36,performs the compression by reading the frame picture image from thepicture image processing memory 32. At this time, the JPEG circuit 33,according to the compression level derived by the preliminarycompression, compresses the frame picture image (step S27 of FIG. 6).Since the extent of the spatial redundancy of the frame picture imageand the field picture image are nearly identical, the compression levelof the field picture image can comply with the frame picture image.Accordingly, when compression occurs at this compression level, theframe picture image is compressed to the target data amount.

The frame picture image that is compressed to the target data amount isread and recorded to the flash memory 35 through the data transfercomponent 34 as a compressed picture image file (step S28 of FIG. 6). Atthis time, the compression level at the time of compression is recordedin the header area of the compressed picture image file, together withthe identification name of the file.

According to the operation described above, a taken picture image can berecorded to the flash memory 35.

A description of the operation for reading and reproducing a pictureimage that has been recorded in the flash memory 35 will now beprovided. The CPU 36 determines whether the read switch SW3 of theoperation switches 37 is pressed, and when the read switch SW3 ispressed (step S6 of FIG. 4), the read routine, to be describedhereafter, is executed (step S7 of FIG. 4).

As an example, assume the four compressed picture image files a throughd are recorded in the flash memory 35. One of the compressed pictureimage files is selected by use of the picture image selection switchSW4. The CPU 36 reads the selected compressed picture image file fromthe flash memory 35 through the data transfer component 34 and transfersit to the picture image processing memory 32 (step S31 of FIG. 7). Atthis time, the CPU 36 reads the compression level used at the time ofcompression from the header area of the compressed picture image file.

The start expansion (decompression) command and the compression levelinformation of the compressed picture image file are transferred fromthe CPU 36 to the JPEG circuit 33, where the JPEG circuit 33 performsthe expansion process of the compressed picture image according to thefollowing procedure in the following order: variable length decoding,followed by reverse quantization, followed by reverse DCT (step S32 ofFIG. 7). At this time, the JPEG circuit 33, for reverse quantization,executes the expansion process that corresponds to the compression levelused by the quantization table that was used at the time ofquantization.

The frame picture image that is restored (decompressed) by the JPEGcircuit 33 is stored in the picture image processing memory 32. The CPU36 outputs the stop output command of the analog projected image signalto the encoder 27. The encoder 27, according to such command, stops thereading of the field picture image that is stored in the picture imagememory 26, and the output of the analog projected image signal isstopped to the monitor 29 (step S33 of FIG. 7).

The picture image processing circuit 31 divides the restored framepicture image into an even number field picture image and an odd numberfield picture image, thereby creating two picture image fields, whichare transferred to the picture image memory 26 (step S34 of FIG. 7). Theencoder 27, by means of the restart output command of the analogprojected image signal from the CPU 36, reads the even number fieldpicture image and the odd number field picture image that are stored inthe picture image memory 26, and D/A converts these to a sequentialanalog projected image signal, which is output to the monitor 29 (stepS35 of FIG. 7).

According to the process described above, the compressed picture imageis restored and displayed on the monitor 29. In this way, the electronicstill camera of the first embodiment derives the compression level byperforming preliminary compression by way of a field picture image,which has a small data amount. Then, compression of the frame pictureimage is performed with the derived compression level. Accordingly,since compression is never repeated with a frame picture image, whichhas a large data amount, the load on the hardware can be reduced, andthe time until the frame picture image is compressed to the target dataamount can be shortened.

More specifically, with the electronic still camera of the presentembodiment, since a photographic picture image can be compressed andrecorded in an extremely short period of time, it becomes possible toimprove successive photography speed when performing successivephotography.

In the first embodiment, the output of the CCD sensor 24 was the fieldpicture image, however, in a second embodiment, the output of the CCDsensor 24 will be the frame picture image. Furthermore, the pictureimage compression process is performed according to a program that isstored in a recording medium (ROM card 45, see FIG. 10).

FIG. 10 is a block diagram of the second embodiment. In FIG. 10, a mainbody 21 is attached to a camera component 22. Within the cameracomponent 22 are a photographic lens 23 and a CCD sensor 24, which isarranged in a position to receive transmitted light of the photographiclens 23. The photo-electric signal of the CCD sensor 24 is input,through the A/D converter 25, into the picture image memory 26 arrangedwithin the main body 21.

The output of the picture image memory 26 is input into the pictureimage processing circuit 38, and a first input/output terminal of thepicture image processing circuit 38 is connected to the video memory 39.Further, the output of the video memory 39 is input into the videoselection switch 28 through the encoder 27. The output of the videoselection switch 28 is input into the monitor 29 or the video terminal30.

The second input/output terminal of the picture image processing circuit38 is connected to the flash memory 35 through the picture imageprocessing memory 32, the JPEG circuit 33 and the data transfercomponent 34. Picture image data is transferred in both directionsbetween the picture image processing circuit 38 and the flash memory 35.

Further, the CPU 40 is arranged within the main body 21, and the controloutput of the CPU 40 is input into the CCD sensor 24, the encoder 27,the JPEG circuit 33, the data transfer component 34 and the pictureimage processing circuit 38. In addition, the CPU 40 receives the outputsignals of the JPEG circuit 33, the data transfer component 34 and theoperation switches 37.

Further, in the main body 21, the ROM card 45 is arranged so as to beable to be freely removed and attached. The output of the ROM card 45 isinput into the data transfer component 34. In addition, a camera controlprogram is stored in the ROM card 45.

The corresponding relationship between the high-level representation ofthe invention in FIG. 1 and the second embodiment is as follows. Thepicture image creation means 1 corresponds to the picture imageprocessing circuit 38 and the video memory 39. The data amountdetermination means 2 corresponds to the CPU 40. The preliminarycompression means 3 corresponds to the JPEG circuit 33. The compressionmeans 4 also corresponds to the JPEG circuit 33. The picture imagecompression processing program is stored on ROM card 45.

A description of the operation of the second embodiment is now provided.

When the power switch (not shown in the figure) is switched ON, the CPU40, through the data transfer component 34, reads the camera controlprogram that is stored in the ROM card 45 and executes the followingoperations according to the program.

The CPU 40 initializes the system after clearing the picture imageprocessing memory 32 and the video memory 39. The start photographycommand is input from the CPU 40 into the CCD sensor 24 and photographybegins. The photographic object obtained through the photographic lens23 is formed on the CCD sensor 24 and converted photo-electrically. Thephoto-electric signal is read in sequence and converted into a digitalvideo signal by the A/D converter 25. In the picture image memory 26,the digital video signal is accumulated in the order received, therebycreating the frame picture image.

The picture image processing circuit 38 divides the frame picture imagethat is stored in the picture image memory 26 into an even number fieldpicture image and an odd number field picture image by reading thepicture element of every other scanning line. This is illustrated inFIG. 9.

The even number field picture image and the odd number field pictureimage that were divided by the picture image processing circuit 38 areaccumulated and stored in sequence in the video memory 39.

The encoder 27 sequentially reads the even number field picture imageand the odd number field picture image that are stored in the videomemory 39, and then D/A converts them to an analog projected imagesignal, and outputs them to the video terminal 30 or the monitor 29 thatis selected by the video selection switch 28. In this instance, themonitor 29 is selected.

Through the operation described above, when the power switch is switchedON, the picture image is taken-in regularly and sequentially displayedon the monitor 29. In this state, the CPU 40 determines whether therelease switch SW1 of the operation switches 37 has been pressed. If therelease switch SW1 is pressed, the following release routine isexecuted.

The CPU 40 outputs the stop output command of the analog projected imagesignal to the encoder 27. The encoder 27 stops, in accordance with sucha command, reading the field picture image that is stored in the videomemory 39, and temporarily stops the output of the analog projectedimage signal to the monitor 29. Next, at the moment that the releaseswitch SW1 is pressed, the image formed on the CCD sensor 24 isaccumulated and stored to the picture image memory 26 through the A/Dconverter 25. The picture image processing circuit 38 divides the framepicture image that is stored in the picture image memory 26 into an evennumber field picture image and an odd number field picture image byreading the picture element of every other scanning line, and the twopicture image fields are transferred to the video memory 39.

The CPU 40 outputs the restart output command of the analog projectedimage signal to the encoder 27, and the encoder 27 reads the even numberfield picture image and the odd number field picture image that arestored in the video memory 39, and D/A converts each of these to ananalog projected image signal, and then outputs it to the monitor 29.

According to the operation described above, the operator has the abilityto take in a picture image at the moment there is a photographicopportunity by pressing the release switch SW1.

A description of the operation that records the taken picture image intothe flash memory 35 is now described. The CPU 40 determines whether therecording switch SW2 of the operation switches 37 is pressed, and whenthe recording switch SW2 is pressed, the following recording routine isexecuted.

Picture image processing circuit 38, according to the field pictureimage creation command from the CPU 40, divides the frame picture imagethat is stored in the picture image memory 26 into an even number fieldpicture image and an odd number field picture image and stores them inthe video memory 39. Picture image processing circuit 38, according tothe field picture image reading command from the CPU 40, selects one ofthe two fields from the video memory 39, and transfers it to the pictureimage processing memory 32. The CPU 40, for example, is set in advanceso as to compress a several MB frame picture image to a target dataamount of about 100 KB. In addition, since the field picture image isthe data amount of ½ of the frame picture image, the CPU 40 is set inadvance so as to compress the field picture image to a preliminarycompression target data amount of 50 KB.

Although the preliminary compression target data amount is set inadvance in the CPU 40 as an alternative, the CPU 40 may also be set upto read the data amount of the field picture image and the frame pictureimage and compute directly by way of the expression (preliminarycompression target data amount)=(target data amount)×(data amount of thefield picture image)/(data amount of the frame picture image).

The JPEG circuit 33 repeats the compression process until the fieldpicture image that is stored in the picture image processing memory 32becomes the preliminary compression target data amount. Furthermore,since the specifics of the preliminary compression that takes place inthe picture image processing memory 32 and the JPEG circuit 33 hasalready been described above in the first embodiment, furtherexplanation will be omitted here. The preliminary compression isperformed of the field picture image, and when the compression level isdetermined, the picture image processing circuit 38 transfers the framepicture image stored in the picture image memory 26 to the picture imageprocessing memory 32 by following the frame picture image readingcommand from the CPU 40.

The JPEG circuit 33, according to the start ma-n compression commandfrom the CPU 40, performs compression by reading the frame picture imagefrom the picture image processing memory 32. At this time, the JPEGcircuit 33 compresses the frame picture image in accordance with thecompression level derived by the preliminary compression. The framepicture image that is compressed to the target data amount is read andrecorded to the flash memory 35 through the data transfer component 34as a compressed picture image file.

According to the operation described above, a taken picture image can berecorded to the flash memory 35.

A description of the operation for reading and reproducing a pictureimage that has been recorded in the flash memory 35 is now provided. TheCPU 40 determines whether the read switch SW3 of the operation switches37 is pressed, and when the read switch SW3 is pressed, the read routineto be described hereafter is executed.

A compressed picture image file is read from the flash memory 35, and isexpanded to the frame picture image by the JPEG circuit 33. Since thespecifics of the operation to store into the picture image processingmemory 32 have already been described in the first embodiment, furtherexplanation will be omitted here.

The CPU 40 outputs the stop output command of the analog projected imagesignal to the encoder 27. The encoder 27, according to such command,stops the reading of the field picture image that is stored in the videomemory 39. The picture image processing circuit 38 divides the framepicture image that is stored in the picture image processing memory 32into an even number field picture image and an odd number field pictureimage, thereby creating two picture image fields that are transferred tothe video memory 39.

The encoder 27, by means of the restart output command of the analogprojected image signal from the CPU 40, reads the even number fieldpicture image and the odd number field picture image that are stored inthe video memory 39, and D/A converts them to a sequential analogprojected image signal where it is output to the monitor 29.

According to the process described above, the compressed picture imageis restored and displayed on the monitor 29. The second embodiment hasthe same result as the first embodiment.

In a third embodiment, preliminary compression will be performed byusing a thumbnail picture image, rather than a field picture image. FIG.11 is a block diagram of the third embodiment.

In FIG. 11, a main body 21 is attached to a camera component 22. Withinthe camera component 22 are a photographic lens 23 and a CCD sensor 24,which is arranged in a position to receive transmitted light of thephotographic lens 23. The photo-electric signal of the CCD sensor 24 isinput, through the A/D converter 25, into the picture image memory 26,which is arranged within the main body 21.

The output of the picture image memory 26 is input into the pictureimage processing circuit 38. The output terminal of the picture imageprocessing circuit 38 is connected to the input terminal of the videomemory 39. Further, the output of the video memory 39 is input into thevideo selection switch 28 through the encoder 27. The output of thevideo selection switch 28 is input into the monitor 29 or the videoterminal 30.

The input/output terminal of the picture image memory 26 is connected tothe input/output terminal of the picture image processing circuit 41,which is arranged within the main body 21. The picture image processingcircuit 41 transfers picture image data in both directions between thepicture image processing memory 32 and the frame memory 42. The pictureimage processing memory 32 is connected to the flash memory 35 throughthe JPEG circuit 33 and the data transfer component 34. Picture imagedata is transferred in both directions between the picture imageprocessing memory 32 and the flash memory 35.

Further, the CPU 43 is arranged within the main body 21. The controloutput of the CPU 43 is input into the CCD sensor 24, the encoder 27,the JPEG circuit 33, the data transfer component 34 and the pictureimage processing circuit 41. The output signals of the JPEG circuit 33,the data transfer component 34 and the operation switches 44 are inputinto the CPU 43.

Further, in the main body 21, the ROM card 45 is arranged so as to beable to be freely removed and attached. The output of the ROM card 45 isinput into the data transfer component 34. In addition, in this ROM card45 is stored the camera control program.

The corresponding relationship between the high-level representation ofthe invention in FIG. 1 and the third embodiment is as follows. Thepicture image creation means 1 corresponds to the picture imageprocessing circuit 41 and the frame memory 42. The data amountdetermination means 2 corresponds to the CPU 43. The preliminarycompression means 3 corresponds to the JPEG circuit 33. The compressionmeans 4 also corresponds to the JPEG circuit 33.

FIG. 12 through FIG. 16 are flow charts describing the operation of thethird embodiment. A description of the operation of the third embodimentis provided hereafter with reference to the figures.

When the power switch (not shown in the figure) is switched ON, the CPU43, through the data transfer component 34, reads the camera controlprogram stored in the ROM card 45 and executes the following operationaccording to such program.

After clearing the picture image memory 26, the picture image processingmemory 32, the video memory 39, and the frame memory 42, the CPU 43initializes the system (step S41 in FIG. 12).

The switch SW5 of the operation switches 44 is a mode switch thatswitches between the photographic mode and the single-view display mode.The CPU 43 determines which of these modes is currently selected (stepS42 of FIG. 12).

When in the photographic mode, the start photography command is inputfrom the CPU 43 into the CCD sensor 24 and photography begins. Moreover,the picture image is taken regularly, and since the description of theoperation for sequential display on the monitor 29 was already given inthe first and second embodiments, further description will be omittedhere.

The CPU 43 determines whether the release switch SW1 of the operationswitches 44 has been pressed. If the release switch SW1 is pressed (stepS44 of FIG. 12), the following release routine is executed (step S45 ofFIG. 12).

The CPU 43 outputs the stop output command of the analog projected imagesignal to the encoder 27. The encoder 27 stops, according to suchcommand, reading the field picture image that is stored in the videomemory 39, and temporarily stops the output of the analog projectedimage signal to the monitor 29 (step S51 of FIG. 13). Next, at themoment that the release switch SW1 is pressed, the image formed on theCCD sensor 24 is accumulated and stored to the picture image memory 26through the A/D converter 25 (step S52 of FIG. 13).

The picture image processing circuit 38 divides the frame picture imagethat is stored in the picture image memory 26 into an even number fieldpicture image and an odd number field picture image by reading thepicture element of every other scanning line. The two picture imagefields are transferred to the video memory 39 (step S53 of FIG. 13).

The CPU 43 outputs the restart output command of the analog projectedimage signal to the encoder 27, and the encoder 27 reads the even numberfield picture image and the odd number field that are stored in thevideo memory 39, and D/A converts each of these to the analog projectedimage signal, and then outputs it to the monitor 29 (step S54 of FIG.13).

According to the operation described above, the operator has the abilityto take in a picture image at the moment there is a photographicopportunity by pressing the release switch SW1.

Next, a description of the operation that records the taken pictureimage into the flash memory 35 will be described. The CPU 43 determineswhether the recording switch SW2 of the operation switches 44 ispressed. When the recording switch SW2 is pressed (step S46 of FIG. 12),the following recording routine is executed (step S47 of FIG. 12).

The picture image processing circuit 41, according to the thumbnailpicture image creation command from the CPU 43, reads the frame pictureimage that is stored in the picture image memory 26, and, as shown inFIG. 17, creates the ¼ reduced-size picture image. This reduced-sizepicture image is a thumbnail picture image for single-view display use.It is not limited to a ¼ reduction. First, the picture image data isextracted from the frame picture image by every other scanning line.Next, every other picture element from each line of picture image datathat was extracted is thinned, thereby creating a ¼ reduced-size pictureimage. The thumbnail picture image created from the picture imageprocessing circuit 41 is mapped to a prescribed address in the framememory 42 (step S61 of FIG. 14).

Next, the picture image processing circuit 41 reads the thumbnailpicture image that is stored in the frame memory 42 and transfers thatto the picture image processing memory 32 (step S62 of FIG. 14).

The CPU 43, for example, is set in advance so as to compress a severalMB frame picture image to a target data amount of about 100 KB. Inaddition, since the thumbnail picture image is the data amount of ¼ ofthe frame picture image, the CPU 43 is set in advance so as to compressthe thumbnail picture image to a preliminary compression target dataamount of 25 KB. Although the preliminary compression target data amountis set in advance in the CPU 43, as an alternative, the CPU 43 may alsobe set up to read the data amount of the thumbnail picture image and theframe picture image and compute directly by means of the expression(preliminary compression target data amount)=(target data amount)×(dataamount of the thumbnail picture image)/(data amount of the frame pictureimage).

The JPEG circuit 33 repeats the compression process until the thumbnailpicture image stored in the picture image processing memory 32 iscompressed to the preliminary compression target data amount. In thisinstance, a description of the specific numerical value will be givenrelative to the preliminary compress process. For example, the dataamount of the thumbnail picture image becomes 250 KB (with a framepicture image of 1 MB).

The preliminary compression target data amount and the preliminarycompression initiation command are transferred from the CPU 43 to theJPEG circuit 33. The JPEG circuit 33, according to such command, readsthe thumbnail picture image that is stored in the picture imageprocessing memory 32 and begins the compression. The JPEG circuit 33reads the data amount of the thumbnail picture image that is stored inthe picture image processing memory 32 and compresses such data amountso that it matches the preliminary compression target data amount. Inthis instance, since a 250 KB data amount must be compressed so as tobecome 25 KB, first, compression is performed at a compression level of30 (expected compression ratio 10%).

The picture image compression is performed by performing the followingsteps in the following order: DCT, followed by linear quantization,followed by variable length coding (step S63 in FIG. 14). JPEG circuit33 repeats the compression by changing the compression level until thecompression result is within a range of 25 KB± an allowable value,thereby deriving the compression level when arriving within this range(steps S64 and S65 of FIG. 14).

For example, when the compression result is 20 KB, since the compressionlevel is too large and there is the possibility that the picture imagewill deteriorate upon reproduction, the compression level is lowered.According to expression (1) described above, an expected compressionratio for the next time is computed to be 12.5%. The JPEG circuit 33performs compression again at the compression level that corresponds tothis expected compression ratio, and it then determines whether thecompression result has become 25 KB.

In addition, when the compression result is 30 KB, since the compressionlevel is too small, an expected compression ratio of 8.3% is computed bythe aforementioned expression (1). Then, the compression is performedagain at the compression level that corresponds to this expectedcompression ratio, and it is determined whether the compression resulthas become 25 KB.

The change of the compression level is executed by appropriatelyadopting, from a quantization table having different quantizationamounts stored in the internal memory of the JPEG circuit 33, aquantization amount for the desired compression level.

The JPEG circuit 33 repeats the feed back process described above, andthe compression level that compresses the thumbnail picture image to thepreliminary compression target data amount is derived. The CPU 43 storesthat compression level in the internal memory (step S66 of FIG. 14).

Next, the picture image processing circuit 41, by means of the framepicture image reading command from the CPU 43, transfers the framepicture image that is stored and accumulated in the picture image memory26 to the picture image processing memory 32 (step S67 of FIG. 14). TheJPEG circuit 33, according to the start main compression command fromthe CPU 43, performs compression by reading the frame picture image fromthe picture image processing memory 32. At this time, the JPEG circuit33, according to the compression level derived by the preliminarycompression, compresses the frame picture image (step S68 of FIG. 14).Since the extent of the spatial redundancy of the frame picture imageand the thumbnail picture image are nearly identical, the compressionlevel of the thumbnail picture image can comply with the frame pictureimage. Accordingly, when compression occurs at this compression level,the frame picture image is compressed to the target data amount.

The frame picture image that is compressed to the target data amount isread and recorded to the flash memory 35 through the data transfercomponent 34 as a compressed picture image file (step S69 of FIG. 14).At this time, in the header area of the compressed picture image file,together with the identification name of the file, the compression levelat the time of compression as well as the identification name of thecorresponding thumbnail picture image are recorded.

According to the operation described above, a taken picture image can berecorded to the flash memory 35.

Next, a description of the operation for reading and reproducing fordisplay a picture image that has been recorded in the flash memory 35will be provided hereafter. The CPU 43 determines the mode status of themode switch SW5. When switching to the single-view display mode, thesingle-view display routine to be described hereafter is executed (stepS43 of FIG. 12).

The picture image processing circuit 41, according to the thumbnailpicture image reading command from the CPU 43, reads the thumbnailpicture image that is stored in the frame memory 42, and transfers it tothe picture image memory 26 (step S71 of FIG. 15). The encoder 27,according to the stop output command of the analog projected imagesignal from the CPU 43, stops the reading of the field picture imagefrom the video memory 39 (step S72 of FIG. 15)

The picture image processing circuit 38, divides the thumbnail pictureimage that is stored in the picture image memory 26 into the even numberfield picture image and the odd number field picture image by readingthe picture element of every other scanning line, and these two pictureimage fields are transferred sequentially to the video memory 39 (stepS73 of FIG. 15). The encoder 27, according to the restart output commandof the analog projected image signal from the CPU 43, D/A converts theeven number field picture image and the odd number field picture imageof the thumbnail picture image that is stored in the video memory 39,and displays it on the monitor 29 that is selected by the videoselection switch 28 (step S74 of FIG. 15). The thumbnail picture imageis displayed on the monitor 29 by means of the operation describedabove.

In addition, when the thumbnail selection switch SW6 is pressed in thisstate, the CPU 43, according to the pressing operation, selects thethumbnail picture image (step S75 of FIG. 15). For example, when thereare 4 thumbnail picture images as shown in FIG. 18, the CPU 43 upon eachpressing of the SW6, selects the thumbnail picture image in the sequenceof A, then B, then C, then D, and changes exterior frame display of thethumbnail picture image that is selected. In this way, following thedirections of the CPU 43, the picture image processing circuit 41creates the thumbnail picture image by adjusting the exterior frame ofthe thumbnail picture image that is selected.

When turning on the read switch SW3 when the thumbnail picture image isin the selected status (step S76 of FIG. 15), the CPU 43, based on theidentification name of the selected thumbnail picture image, reads thecorresponding compressed picture image file through the data transfercomponent 34 where it is transferred to the picture image processingmemory 32 (step S77 of FIG. 16). At this time, the CPU 43 reads thecompression level at the time of compression from the header area of thecompressed picture image file.

The start expansion command and the compression level information of thecompressed picture image file are transferred from the CPU 43 to theJPEG circuit 33. The JPEG circuit 33 performs the expansion process ofthe compressed picture image as described previously. At this time, theJPEG circuit 33, for reverse quantization, executes the expansionprocess that corresponds to the compression level used by thequantization table that was used at the time of compression.

The frame picture image that is expanded is stored and accumulated inthe picture image processing memory 32. The picture image processingcircuit 41 transfers such frame picture image to the picture imagememory 26 (step S78 of FIG. 16).

The CPU 43 outputs the stop output command of the analog projected imagesignal to the encoder 27. The encoder 27 stops the reading of the fieldpicture image from the video memory 39 (step S79 of FIG. 16). Thepicture image processing circuit 38 divides the frame picture image ofthe picture image memory 26 into two fields of picture images, and thentransfers them to the video memory 39 (step S80 of FIG. 16). The encoder27, in accordance with the restart output command of the analogprojected image signal from the CPU 43, D/A converts the even numberfield picture image and the odd number field picture image that arestored in the video memory 39 to a sequential analog projected imagesignal where it is then output to the monitor 29 (step S81 of FIG. 16).

In accordance with the process described above, the operator can, byselecting the desired picture image from within a group of single-viewdisplay thumbnail picture images, reproduce and display such pictureimage onto the monitor 29.

In this way, in the third embodiment, the compression level is derivedby performing preliminary compression on a thumbnail picture image forsingle-view display, and compressing the frame picture image accordingto such compression level. Accordingly, the compression process for aframe picture image with a large data amount is completed in oneattempt, thereby making possible the compression of a frame pictureimage to a target data amount in a short period of time.

Moreover, in the present invention, an explanation using an electronicstill camera as the example which employs the picture image compressionapparatus of the present invention. However, the photographic componentis not a necessary component of the device. In other words, the presentinvention may also compress picture image data created externally. Forexample, the compression process may also be applied to a picture imagedata read into an image scanner, transferred from an external source, orso forth.

Furthermore, in the present embodiment, a flash memory was used as themedium to record the compressed picture image. However, without beinglimited to that, the invention may also use a magnetic recording medium,an optical recording medium, and a magnetooptical recording medium, forexample. In addition, the picture image compression processing programand the compressed picture image are recorded in individual recordingmediums. They may also be recorded into the same recording medium.

Further, in the present embodiment, in the case where the extent ofspatial redundancy of the frame picture image and the reduced-sizepicture image is different, there will be cases when the compressionresult of the frame picture image does not match to the target dataamount. At this time, the frame picture image may be compressed directlyso as to match the target data amount. Furthermore, the preliminarycompression target data amount may also be adjusted to correspond toeither target data amount or the compression result of the frame pictureimage, thereby making a match with the target data amount by performingagain preliminary compression followed by compression of the framepicture image.

Furthermore, any one portion of the frame picture image may also becut-out as the method of creating the reduced-size picture image.

In addition, in the third embodiment, the thumbnail picture image itselfmay also be compressed by the JPEG circuit 33 and recorded into theflash memory 35. By so doing, the frame memory 42 for the recording ofthe thumbnail picture image can be an inexpensive memory such as a DRAM.

In addition, while the description in the present embodiment used theJPEG, MPEG may also be used as the compression method. Various othercompression techniques, such as, for example, wavelet and fractalcompression, can be used with the invention. Rather than Huffman coding,the variable length coding can be, for example, run-length coding, LZW,and/or minimum redundancy coding.

Although the described embodiments used a CCD as the image pickup, otherphotosensors could be used. For example, a CMOS device or a PSD(Photo-Sensitive-Diode) also can be used as the image pickup.

In the illustrated embodiment, the camera controller (the CPU andassociated circuitry) is implemented using a suitably programmed generalpurpose computer, e.g., a microprocessor, microcontroller or otherprocessor device (CPU or MPU). It will be appreciated by those skilledin the art, that the controller can also be implemented as a singlespecial purpose integrated circuit (e.g., ASIC) having a main or centralprocessor section for overall, system-level control, and separatesections dedicated to performing various different specificcomputations, functions and other processes under control of the centralprocessor section. The controller can also be implemented using aplurality of separate dedicated or programmable integrated or otherelectronic circuits or devices (e.g., hardwired electronic or logiccircuits such as discrete element circuits, or programmable logicdevices such as PLDs, PLAs, PALs or the like). The controller can alsobe implemented using a suitably programmed general purpose computer inconjunction with one or more peripheral (e.g., integrated circuit) dataand signal processing devices. In general, any device or assembly ofdevices on which a finite state machine capable of implementing the flowcharts shown in FIGS. 4–7 and/or 12–16 can be used as the controller.

As noted earlier, the invention further includes, as another aspect, acarrier wave encoded with the control program (described above) that isreadable by the controller (a computer) to control the camera tofunction as described above. The carrier wave can be transmitted over acommunications network such as, for example, the World Wide Web, and/ortransmitted in a wireless fashion, for example, by radio waves or byinfrared waves. Additionally, or alternatively, the carrier wave can befixed in a computer-readable recording medium, such as, for example, aCD-ROM, a computer hard drive, RAM, or other types of memories that arereadily removable or intended to remain fixed within the computer. Onesuch memory is the ROM card 45.

Additionally, and as noted earlier, the invention can be implemented inapparatus other than a camera. That is, the device that performs theimage processing need not be capable of creating an electronic pictureimage. The electronic picture image simply can be input to the imageprocessing apparatus.

While the present invention has been described with reference topreferred embodiments thereof, it is to be Understood that the inventionis not limited to the disclosed embodiments or constructions. To thecontrary, the invention is intended to cover various modifications andequivalent arrangements. In addition, while the various elements of thedisclosed invention are shown in various combinations andconfigurations, which are exemplary, other combinations andconfigurations, including more, less or only a single element, are alsowithin the spirit and scope of the invention.

1. A picture image compression apparatus that compresses data of apicture image to a predetermined target data amount, comprising: pictureimage creation means for creating, from the picture image, areduced-size picture image having a reduced number of picture elementsof the picture image; preliminary compression means for compressing thereduced-size picture image to a preliminary compression target dataamount related to the predetermined target data amount by transformingthe reduced-size picture image, quantizing the transformed reduced-sizepicture image, and coding the quantized reduced-size picture image; andcompression means for compressing the picture image to the predeterminedtarget data amount by transforming the picture image, quantizing thetransformed picture image, and coding the quantized picture image;wherein the preliminary compression means derives a compression level ofthe picture image, based on a compression ratio when the reduced-sizepicture image is compressed to the preliminary compression target dataamount; and wherein the compression means compresses the picture imageto the predetermined target data amount, based on the compression levelderived by the preliminary compression means.
 2. The picture imagecompression apparatus of claim 1, wherein the picture image creationmeans creates a field picture image as the reduced-size picture image.3. The picture image compression apparatus of claim 1, wherein thepicture image creation means creates a thumbnail picture image as thereduced-size picture image.
 4. The picture image compression apparatusof claim 3, wherein a plurality of the thumbnail picture images arecapable of being displayed in a single-view display.
 5. The pictureimage compression apparatus of claim 1, wherein the preliminarycompression means derives the compression level by repeatedlycompressing the reduced-size picture image using different compressionlevels until a compression level is used that results in the preliminarycompression target data amount being obtained.
 6. The picture imagecompression apparatus of claim 1, wherein the preliminary compressionmeans and the compression means perform compression by omittingredundant data from the picture image and the reduced-size pictureimage.
 7. The picture image compression apparatus of claim 1, furthercomprising data amount determination means for deriving the preliminarycompression target data amount from the predetermined target dataamount.
 8. The picture image compression apparatus of claim 7, whereinthe data amount determination means also derives the preliminarycompression target data amount from a ratio between data amounts of thepicture image and the reduced-size picture image.
 9. The picture imagecompression apparatus of claim 1, wherein the picture image compressionapparatus is an electronic camera having picture image input means forphotoelectrically converting an object image into the data of thepicture image.
 10. The picture image compression apparatus of claim 1,wherein the preliminary compression target data amount is less than thepredetermined target data amount.
 11. A picture image compressionapparatus that compresses data of a picture image to a predeterminedtarget data amount, comprising: a picture image processor that creates,from the picture image, a reduced-size picture image having a reducednumber of picture elements of the picture image; a compression circuitthat compresses the reduced-size picture image to a preliminarycompression target data amount related to the predetermined target dataamount by transforming the reduced-size picture image, quantizing thetransformed reduced-size picture image, and coding the quantizedreduced-size picture image; and a controller that compresses the pictureimage to the predetermined target data amount by transforming thepicture image, quantizing the transformed picture image, and coding thequantized picture image; wherein the compression circuit derives acompression level of the picture image, based on a compression ratiowhen the reduced-size picture image is compressed to the preliminarycompression target data amount; and wherein the controller compressesthe picture image to the predetermined target data amount, based on thecompression level derived by the compression circuit.
 12. The pictureimage compression apparatus of claim 11, wherein the picture imageprocessor creates a field picture image as the reduced-size pictureimage.
 13. The picture image compression apparatus of claim 11, whereinthe picture image processor creates a thumbnail picture image as thereduced-size picture image.
 14. The picture image compression apparatusof claim 11, wherein the compression circuit performs compression byomitting redundant data from the picture image that is to be compressed.15. The picture image compression apparatus of claim 14, wherein thecompression circuit is a JPEG compression circuit.
 16. The picture imagecompression apparatus of claim 11, wherein the picture image compressionapparatus is an electronic camera having a photoelectric converter thatconverts an object image into the data of the picture image.
 17. Thepicture image compression apparatus of claim 11, wherein the preliminarycompression target data amount is less than the predetermined targetdata amount.
 18. A method of determining a compression level to be usedto compress data of a picture image to a predetermined target dataamount, comprising the steps of: creating, from the picture image, areduced-size picture image having a reduced number of picture elementsof the picture image; compressing the reduced-size picture image to apreliminary compression target data amount related to the predeterminedtarget data amount by transforming the reduced-size picture image,quantizing the transformed reduced-size picture image, and coding thequantized reduced-size picture image; and compressing the picture imageto the predetermined target data amount by transforming the pictureimage, quantizing the transformed picture image, and coding thequantized picture image; wherein compressing the reduced-size pictureimage comprises deriving a compression level of the picture image, basedon a compression ratio when the reduced-size picture image is compressedto the preliminary compression target data amount; and whereincompressing the picture image comprises compressing the picture image tothe predetermined target data amount, based on the derived compressionlevel.
 19. The method of claim 18, further comprising the step ofcompressing the data of the picture image to the predetermined targetdata amount using the derived compression level.
 20. The method of claim18, wherein the reduced-size picture image is a field picture image. 21.The method of claim 18, wherein the reduced-size picture image is athumbnail picture image.
 22. The method of claim 18, wherein the step ofderiving the compression level includes repeatedly compressing thereduced-size picture image using different compression levels until acompression level is used that results in the preliminary compressiontarget data amount being obtained.
 23. The method of claim 18, furthercomprising deriving the preliminary compression target data amount fromthe predetermined target data amount.
 24. The method of claim 23,wherein the preliminary compression target data amount also is derivedfrom a ratio between data amounts of the picture image and thereduced-size picture image.
 25. The method of claim 18, wherein thepreliminary compression target data amount is less than thepredetermined target data amount.
 26. A computer-readable recordingmedium encoded with a computer executable control program fordetermining a compression level to be used to compress data of a pictureimage to a predetermined target data amount, the control programincluding instructions for: creating, from the picture image, areduced-size picture image having a reduced number of picture elementsof the picture image; compressing the reduced-size picture image to apreliminary compression target data amount related to the predeterminedtarget data amount by transforming the reduced-size picture image,quantizing the transformed reduced-size picture image, and coding thequantized reduced-size picture image; and compressing the picture imageto the predetermined target data amount by transforming the pictureimage, quantizing the transformed picture image, and coding thequantized picture image; wherein compressing the reduced-size pictureimage comprises deriving a compression level of the picture image, basedon a compression ratio when the reduced-size picture image is compressedto the preliminary compression target data amount; and whereincompressing the picture image comprises compressing the picture image tothe predetermined target data amount, based on the derived compressionlevel.
 27. The computer-readable recording medium of claim 26, whereinthe control program further includes instructions for compressing thedata of the picture image to the predetermined target data amount usingthe derived compression level.
 28. The computer-readable recordingmedium of claim 26, wherein the creating instruction is to create thereduced-size picture image by creating a field picture image.
 29. Thecomputer-readable recording medium of claim 26, wherein the creatinginstruction is to create the reduced-size picture image by creating athumbnail picture image.
 30. The computer-readable recording medium ofclaim 26, wherein the instruction to derive the compression levelincludes an instruction to repeatedly compress the reduced-size pictureimage using different compression levels until a compression level isused that results in the preliminary compression target data amountbeing obtained.
 31. The computer-readable recording medium of claim 26,further comprising an instruction to derive the preliminary compressiontarget data amount from the predetermined target data amount.
 32. Thecomputer-readable recording medium of claim 31, wherein the preliminarycompression target data amount also is derived from a ratio between dataamounts of the picture image and the reduced-size picture image.
 33. Thecomputer-readable recording medium of claim 26, wherein the preliminarycompression target data amount is less than the predetermined targetdata amount.
 34. A method for compressing a data amount of picture imagedata of a picture image acquired by an image pickup device, to apredetermined target data amount, comprising: creating a reduced-sizepicture image from the picture image by reducing a number of pictureelements of the picture image; compressing the reduced-size pictureimage to a preliminary compression target data amount related to thepredetermined target data amount by transforming the reduced-sizepicture image, quantizing the transformed reduced-size picture image,and coding the quantized reduced-size picture image; and compressing thepicture image to the predetermined target data amount by transformingthe picture image, quantizing the transformed picture image, and codingthe quantized picture image; wherein compressing the reduced-sizepicture image comprises deriving a compression level of the pictureimage, based on a compression ratio when the reduced-size picture imageis compressed to the preliminary compression target data amount; andwherein compressing the picture image comprises compressing the pictureimage to the predetermined target data amount, based on the derivedcompression level.
 35. A method for compressing a data amount of pictureimage data of a picture image acquired by an image pickup device to apredetermined target data amount, comprising: generating the pictureimage data from the picture image; creating a reduced-size picture imagefrom the picture image data by reducing a number of picture elements ofthe picture image data; compressing the reduced-size picture image to apreliminary compression target data amount related to the predeterminedtarget data amount by transforming the reduced-size picture image,quantizing the transformed reduced-size picture image, and coding thequantized reduced-size picture image; and compressing the picture imageto the predetermined target data amount by transforming the pictureimage, quantizing the transformed picture image, and coding thequantized picture image; wherein compressing the reduced-size pictureimage comprises deriving a compression level of the picture image, basedon a compression ratio when the reduced-size picture image is compressedto the preliminary compression target data amount; and whereincompressing the picture image comprises compressing the picture image tothe predetermined target data amount, based on the derived compressionlevel.